Light-transmitting metal oxides have been used in semiconductor devices. For example, conductive metal oxides (hereinafter referred to as oxide conductors) such as indium tin oxide (ITO) have been used as transparent electrode materials needed in display devices such as liquid crystal displays.
In addition, light-transmitting metal oxides have attracted attention as materials having semiconductor characteristics. For example, In—Ga—Zn—O-based oxides and the like have been expected to be used as semiconductor materials needed in display devices such as liquid crystal displays. In particular, they have been expected to be used for channel layers of thin film transistors (hereinafter also referred to as TFTs).
TFTs which include metal oxides having semiconductor properties (hereinafter referred to as oxide semiconductors) can be formed through low-temperature processes. Thus, expectations for oxide semiconductors as materials which replace or surpass amorphous silicon used in display devices and the like are increased.
Further, the use of oxide conductors and oxide semiconductors having light-transmitting properties allows the production of light-transmitting TFTs (for example, see Reference 1).
Furthermore, TFTs including oxide semiconductors as channel layers have high field effect mobility. Thus, driver circuits of display devices or the like can be formed using the TFTs (for example, see Reference 2).